An Organic Light Emitting Diode (OLED) display receives much attention for its advantages such as low power consumption, high luminance, low cost, wide viewing angle and fast response and the like, and thus it has been widely used in the technical field of organic light-emitting.
However, in the OLED display, there are the following inevitable problems. Firstly, it is possible that a threshold voltage Vth of each of transistors for the displaying of an image on an array substrate drifts due to the non-uniformities in structure, electrical capability and stability which are introduced during the manufacturing process of the array substrate. Secondly, the stability of the transistor would decrease if it were turned on for a long time. In addition, a load of a signal line increases accordingly with the development of a large scale OLED in size, which results in an attenuation in voltage on the signal line, e.g., the changing of an operating voltage.
When an OLED is driven to operate by an existing pixel circuit structure for driving OLED to emit light, the current flowing through the OLED depends on the threshold voltage Vth of a driving transistor, and/or the stability of the driving transistor, and/or a reference voltage VDD. Even if the same driving signal is applied to each pixel, the currents flowing through individual OLEDs on a display area of the array substrate might be unequal to each other, which results in non-uniformity in the luminance of the OLEDs on the array substrate, and thus causes non-uniformity in image luminance.